JP5472471B2 - Digital watermark embedding apparatus, digital watermark embedding method, digital watermark embedding computer program, and digital watermark detection apparatus - Google Patents

Description

  The present invention relates to, for example, a digital watermark embedding device that embeds digital watermark information in moving image data, a digital watermark embedding method, a computer program for embedding digital watermark, and a digital watermark detection device that detects digital watermark information embedded in moving image data About.

In recent years, services for distributing video content such as movies via the Internet have been provided. These video contents are distributed after being encrypted by digital rights management (DRM) technology. Also, DRM technology prohibits unauthorized copying or distribution of these video contents.
However, a case where the viewer illegally duplicates the video content by photographing the video content displayed on the computer display or the television monitor using a photographing device such as a camcorder, and illegally distributes the duplicated video content. Has occurred. Since the video content displayed on the display is not encrypted, it is difficult to prevent the distribution of the video content copied by shooting.

  Therefore, a technique has been developed in which information such as a viewer identification number is embedded in moving image data as a digital watermark in advance. Even if the moving image data embedded with the electronic watermark displayed on the display is shot with a camcorder and illegally copied, the electronic watermark still remains in the copied moving image data. After the distribution of moving image data illegally copied by analog capture, the identification number of the viewer who has illegally used video content is identified by detecting the digital watermark from the copied moving image data. It is possible. Therefore, even when video content is illegally duplicated by analog capture and uploaded to a video posting site or the like, the video content manager may specify the source of the leak from the information embedded in the uploaded video content. it can.

  By the way, it is preferable that the digital watermark is embedded in the moving image data so that the viewer cannot identify the digital watermark embedded in the moving image data. In order to embed a digital watermark in moving image data so that the viewer cannot identify the digital watermark, luminance fluctuation caused by the digital watermark, that is, the value of the pixel in the area where the digital watermark is embedded and the values of the surrounding pixels The difference is preferably small. However, if the pixel value difference between the pixels in the area where the digital watermark is embedded and the surrounding pixels is small, the video data embedded with the digital watermark should be compressed according to standards such as the Moving Picture Experts Group (MPEG). As a result, the digital watermark may be lost. In addition, the digital watermark may be lost due to image distortion or the like when the moving image data in which the digital watermark is embedded is captured by a camcorder or the like. Such a problem does not occur if the pixel value difference between the pixels in the area where the digital watermark is embedded and the surrounding pixels is large, but in this case, the digital watermark can be perceived by the viewer. In other words, there is a trade-off relationship between the magnitude of the spatial pixel value change caused by the digital watermark and the resistance to the digital watermark not disappearing. In order to solve this trade-off problem, various digital watermark techniques have been invented so far (see, for example, Patent Documents 1 to 4).

For example, the additional signal multiplexing apparatus disclosed in Patent Document 1 outputs the main signal by field repetition, outputs the additional signal by field repetition that inverts every field, and multiplexes the main signal and the additional signal.
The digital watermark embedding device disclosed in Patent Document 2 embeds embedded information as an electronic watermark into an input signal having dimensions of N or more. This digital watermark embedding device generates an (N-1) -dimensional pattern based on embedded information, and generates an N-dimensional embedded pattern by modulating a periodic signal according to the value on the (N-1) -dimensional pattern Then, the embedded pattern is superimposed on the input signal. Alternatively, the digital watermark embedding apparatus superimposes the (N-1) dimensional pattern on the (N-1) order plane of a part of the signal obtained by orthogonal transform of the input signal, and the (N-1) dimensional pattern is An orthogonal inverse transform is performed on the superimposed signal.
Furthermore, the digital watermark embedding device disclosed in Patent Document 3 temporally changes the position of the geometric pattern to be embedded for each frame included in the moving image in accordance with the encoded watermark information. This digital watermark embedding device changes the position of the geometric pattern so as to be convex upward or convex downward depending on the value of the watermark information.
Furthermore, the digital watermark embedding method disclosed in Patent Document 4 changes a symbol component included in a digital watermark pattern embedded in each frame, for example, as a spread pattern by spectrum spread for each frame.

JP-A-3-10483 International Publication No. 2007/102403 JP 2004-179744 A JP 2006-270215 A

However, in the technique disclosed in Patent Document 1, an apparatus for detecting a digital watermark emphasizes embedded information by obtaining a difference between frames when detecting embedded information, and detects the emphasized information. . Therefore, the frame of the moving image displayed on the display and the frame of the video camera that captures the moving image data displayed on the display need to be accurately synchronized. However, the display display frame rate and the video camera capture frame rate rarely match exactly. Therefore, there is a high possibility that an apparatus that detects digital watermarks cannot detect digital watermark information from analog captured video data.
Further, the technique disclosed in Patent Document 2 is different from the technique disclosed in Patent Document 1 in that accurate synchronization of frames is unnecessary. Therefore, in the technique disclosed in Patent Document 2, the resistance of digital watermark information to analog capture is improved. However, the technique disclosed in Patent Document 2 has a problem in that noise is stuck to an image, which is called “frosted glass effect”, because the watermark embedding position is always constant.

Further, when several frames are thinned out from moving image data created by analog capture of moving image data in which digital watermark information is embedded using the technique disclosed in Patent Document 3, the upper end of the position of the geometric pattern It becomes difficult to find a reference position in the middle of the lower end. As a result, it becomes difficult to detect a digital watermark. In addition, in order to specify the position of the geometric pattern from the image, the difference between the pixel value of the portion where the geometric pattern is embedded and the surrounding pixel values must be large, resulting in image quality degradation. End up. Furthermore, since an image generally includes many images of an object that moves in parallel, it is difficult to distinguish between the movement of such an image and the movement of the geometric pattern, so that it is difficult to detect the geometric pattern. If a device for detecting a digital watermark fails to detect a geometric pattern in several frames, it becomes difficult to detect the digital watermark as if the frames are thinned out.
Furthermore, in the technique disclosed in Patent Document 4, since the diffusion pattern is different for each frame, an apparatus for detecting a digital watermark needs to estimate the diffusion pattern for each frame, which makes detection of the watermark more difficult.

  Therefore, the present specification describes an electronic watermark in which electronic watermark information is embedded in the moving image data so that the electronic watermark information is not lost even if the moving image data is modified by analog capture or the like, and the viewer cannot view the electronic watermark information. An object is to provide an embedding device.

  According to one embodiment, a digital watermark embedding device is provided. The digital watermark embedding apparatus includes an interface unit that acquires moving image data and digital watermark information, and a processing unit that embeds digital watermark information in the moving image data. The processing unit includes a plurality of pixels, and a watermark pattern to be superimposed on each image in the moving image data includes at least a part of a reference region set at a predetermined position on each image in the moving image data. The watermark moves so as to move according to the value of the symbol with time in the first movement range, and as the watermark pattern moves, the average pixel value of the reference area superimposed by the watermark pattern changes periodically. A watermark pattern position determination function that determines the position of the pattern and a watermark pattern superimposition function that corrects the value of each pixel included in the area where the reference area and the watermark pattern overlap according to the value of the corresponding pixel in the watermark pattern To do.

  According to another embodiment, a digital watermark embedding method is provided. This digital watermark embedding method acquires moving image data and digital watermark information, includes a plurality of pixels, and a watermark pattern to be superimposed on each image in the moving image data is a predetermined pattern on each image in the moving image data. The reference region is moved according to the value of the symbol with time in a first movement range including at least a part of the reference region set at the position, and the reference region superimposed by the watermark pattern is moved with the movement of the watermark pattern. The position of the watermark pattern is determined so that the average pixel value changes periodically, and the value of each pixel included in the region where the reference region and the watermark pattern overlap is corrected according to the value of the corresponding pixel of the watermark pattern. Including that.

  According to still another embodiment, there is provided a computer program that causes a computer to embed digital watermark information in moving image data. The computer program includes a plurality of pixels, and a watermark pattern to be superimposed on each image in the moving image data includes at least a part of a reference area set at a predetermined position on each image in the moving image data. The watermark moves so as to move according to the value of the symbol with time in the first movement range, and as the watermark pattern moves, the average pixel value of the reference area superimposed by the watermark pattern changes periodically. It has an instruction code for determining the position of the pattern and for causing the computer to correct the value of each pixel included in the area where the reference area and the watermark pattern overlap according to the value of the corresponding pixel of the watermark pattern.

According to still another embodiment, a digital watermark detection apparatus is provided. The electronic watermark detection apparatus includes an interface unit that acquires moving image data in which electronic watermark information is embedded, and a processing unit that detects electronic watermark information embedded in the moving image data. This processing unit has a pixel value averaging function for calculating an average pixel value in a reference area set at a predetermined position of each image for each image in the moving image data, and the average pixel value in the reference area has elapsed over time. A watermark pattern corresponding to a symbol included in the digital watermark information and encoded in the error correction code or the error detection code is embedded in each image. The watermark pattern detection function to determine, the watermark phase detection function to determine the phase of the average pixel value change in the reference area, and all symbol patterns that can be taken from the difference in phase are calculated. The symbol value included in the digital watermark information is the symbol value included in the symbol pattern without error when decoding according to the correction code or error detection code. To realize the electronic watermark information extraction function according to the value.
Alternatively, instead of the watermark pattern detection function, the phase detection function, and the digital watermark information extraction function, the processing unit may include symbols included in the digital watermark information when the average pixel value in the reference region varies with time. A watermark pattern detection function that determines that a watermark pattern corresponding to is embedded in each image, and a watermark pattern movement direction detection that identifies the movement direction of the watermark pattern based on the temporal variation of the value of each pixel included in the reference area The symbol included in the digital watermark information includes a value corresponding to the movement direction of the watermark pattern with reference to a reference table that represents the correspondence relationship between the function and the movement direction of the watermark pattern and the value that can be taken by the symbol included in the digital watermark information. And a digital watermark information extraction function with a value of.

The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed.

  The digital watermark embedding device disclosed herein converts the digital watermark information into a moving image so that the digital watermark information is not lost even if the moving image data is modified by analog capture or the like, and the viewer cannot visually recognize the digital watermark information. It can be embedded in image data.

FIG. 1 is a schematic configuration diagram of a digital watermark embedding apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating functions of a processing unit realized for embedding digital watermark information in moving image data according to the first embodiment. FIG. 3A is a diagram illustrating an example of the relationship between the reference region and the watermark pattern. FIG. 3B is a graph showing the change over time of the average value of the pixel values in the reference area, corresponding to FIG. FIG. 4A is a diagram illustrating another example of the relationship between the reference area and the watermark pattern. FIG. 4B is a graph showing the change over time of the average value of the pixel values in the reference area, corresponding to FIG. 5A to 5F are diagrams showing still another example of the relationship between the reference region and the watermark pattern. FIG. 6 is a diagram illustrating still another example of the relationship between the reference region and the watermark pattern. FIG. 7 is an operation flowchart of a digital watermark embedding process controlled by a computer program executed on the processing unit of the digital watermark embedding apparatus according to the first embodiment. FIG. 8 is a block diagram illustrating functions of a processing unit realized for embedding digital watermark information in moving image data according to the second embodiment. FIG. 9 is a diagram illustrating the relationship between the position of each block on the original image and the position of each block in the image after scramble processing. FIG. 10 is a diagram illustrating an example of the relationship between the watermark pattern size and the scramble block size. FIG. 11A is a diagram illustrating an example of a randomly converted image in which a watermark pattern is embedded, and FIG. 11B is an image obtained by performing inverse random conversion on the image illustrated in FIG. FIG. FIG. 12 is an operation flowchart of a digital watermark embedding process controlled by a computer program executed on the processing unit of the digital watermark embedding apparatus according to the second embodiment. FIG. 13 is a block diagram illustrating functions of a processing unit realized for embedding digital watermark information in moving image data according to the third embodiment. FIG. 14A is a diagram showing an example of an image in which a plurality of reference areas including a specific reference area are set, and FIG. 14B is set for the image shown in FIG. It is a graph which shows an example of the time change of the average pixel value in each reference field. FIG. 15 is a schematic configuration diagram of a digital watermark detection apparatus according to one embodiment. FIG. 16 is a block diagram illustrating functions of a processing unit of a digital watermark detection apparatus realized for detecting digital watermark information on moving image data. FIG. 17 is an operation flowchart of a digital watermark detection process controlled by a computer program executed on the processing unit of the digital watermark detection apparatus.

  Hereinafter, a digital watermark embedding device according to each embodiment will be described with reference to the drawings. This digital watermark embedding device is configured to change the area of a region where a watermark pattern indicating that digital watermark information is embedded and a reference region on each image of moving image data overlap with each other in time series. The average value of the pixel values in the region is changed with time.

  Each image included in the moving image data may be either a frame or a field. The frame is one still image in the moving image data, while the field is a still image obtained by extracting only odd-numbered data or even-numbered data from the frame.

  FIG. 1 is a schematic configuration diagram of a digital watermark embedding device according to one embodiment. The digital watermark embedding device 1 includes an interface unit 11, a storage unit 12, and a processing unit 13. The digital watermark embedding device 1 embeds digital watermark information in the moving image data acquired via the interface unit 11.

The interface unit 11 is, for example, a video signal interface for connecting the digital watermark embedding device 1 to a moving image input device (not shown) such as a camcorder or an image display device (not shown) such as a liquid crystal display and its control. It has a circuit. Alternatively, the interface unit 11 may include a communication interface for connecting the digital watermark embedding device 1 to a communication network according to a communication standard such as Ethernet (registered trademark) and a control circuit thereof. Alternatively, the interface unit 11 has a circuit for connecting the antenna for receiving moving image data distributed wirelessly and the digital watermark embedding apparatus 1 and decoding the moving image data received via the antenna.
The interface unit 11 acquires moving image data from the moving image input device or via a communication network or an antenna, and passes the moving image data to the processing unit 13.
Further, the interface unit 11 may include an interface circuit in accordance with a bus standard such as a universal serial bus in order to connect a user interface device such as a keyboard or a mouse to the digital watermark embedding device 1. The interface unit 11 acquires data to be embedded as digital watermark information in the moving image data from the user interface device or the communication network, and passes the data to the processing unit 13.

  The digital watermark information includes, for example, at least one of a viewer identification number, a moving image data distribution source identification number, and an identification number of a video reproduction apparatus in which the digital watermark embedding apparatus 1 is incorporated. Further, in this specification, one of a plurality of numerical values or symbols representing the viewer identification number included in the digital watermark information, for example, one bit is used as a symbol. Therefore, the symbols included in the digital watermark information have any one of a plurality of predetermined different values. For example, if the symbol included in the digital watermark information is a bit, the symbol has a value of “0” or “1”.

  Further, the interface unit 11 receives the moving image data in which the digital watermark information is embedded from the processing unit 13, and outputs the moving image data in which the digital watermark information is embedded to an image display device such as a liquid crystal display. Alternatively, the interface unit 11 may transmit the moving image data in which the digital watermark information is embedded to another device connected to the digital watermark embedding apparatus 1 via a communication network.

  The storage unit 12 includes, for example, at least one of a semiconductor memory, a magnetic disk device, and an optical disk device. The storage unit 12 stores a computer program executed by the digital watermark embedding apparatus 1 and various parameters used for embedding digital watermark information. In addition, the storage unit 12 stores one or more images and digital watermark information included in the moving image data before the digital watermark information is embedded until the processing unit 13 generates the moving image data in which the digital watermark information is embedded. You may memorize | store temporarily. Further, the storage unit 12 may store moving image data in which digital watermark information is embedded.

  The processing unit 13 includes one or a plurality of processors, a memory circuit such as a random access memory, and a peripheral circuit. Then, the processing unit 13 embeds digital watermark information in the moving image data. Further, the processing unit 13 controls the entire digital watermark embedding apparatus 1.

  FIG. 2 is a block diagram showing the function of the processing unit 13 realized for embedding digital watermark information in moving image data. The processing unit 13 includes a watermark pattern position determining unit 21, a watermark pattern superimposing unit 22, and a movement history recording unit 23. Each of these units included in the processing unit 13 is a functional module implemented by a computer program executed on a processor included in the processing unit 13. Alternatively, the watermark pattern position determining unit 21, the watermark pattern superimposing unit 22, and the movement history recording unit 23 may be implemented in the digital watermark embedding apparatus 1 as separate arithmetic circuits.

The processing unit 13 superimposes a watermark pattern having a predetermined shape that periodically moves over time on each image of the moving image data according to the value of the symbol of interest included in the digital watermark information.
In the present embodiment, for example, a reference area having the same shape and the same size as the watermark pattern is set on the image. The watermark pattern moves on the image so that the state overlapping with the reference region and the state not overlapping with the reference region are periodically repeated within a moving range including at least a part of the reference region. For this reason, the fact that the digital watermark information is embedded is represented by the fact that the temporal variation of the average luminance value of the pixels included in the reference area occurs according to the movement cycle of the watermark pattern.

  A plurality of symbols included in the digital watermark information may be embedded in each image in one moving image data. In this case, a plurality of reference areas and watermark patterns are set for each image in the moving image data. Then, one reference area and a watermark pattern that moves within a moving range including the reference area correspond to one symbol.

Further, in the present embodiment, the value of the symbol embedded in the moving image data is represented by the phase difference in the temporal variation of the average pixel value in the reference area. The average pixel value of the reference region periodically repeats light and dark depending on the area of the reference region superimposed by the watermark pattern.
For example, when the average pixel value of one reference region changes from light to dark to light at each time t ₀ , t ₁ , and t ₂ , the symbol at this time is set to “0”. Further, when the average pixel value of another reference area changes to dark, bright, and dark at each time of t ₀ , t ₁ , and t ₂ , the symbol at this time is set to “1”. As described above, the processing unit 13 can change the value of the embedded symbol by making a difference in the phase in the temporal variation of the average pixel value in the reference region. Contrary to the above, the symbol value is set to '1' when the average pixel value of the reference region varies from light to dark to light and to '0' when it varies from dark to light to dark. May be.

In another embodiment, the value of the symbol embedded in the moving image data may be represented by the moving direction of the watermark pattern. Therefore, the watermark pattern position determination unit 21 sets the movement direction and movement range of the watermark pattern according to the value of the symbol of interest included in the digital watermark information.
For example, when the value of the focused symbol is “1”, the watermark pattern position determination unit 21 sets the movement range so that the watermark pattern moves in the vertical direction. On the other hand, when the value of the symbol of interest is “0”, the watermark pattern position determination unit 21 sets the movement range so that the watermark pattern moves in the horizontal direction. The watermark pattern position determination unit 21 sets a movement range so that the watermark pattern moves in the vertical direction when the value of the symbol of interest is “0”, and the value of the symbol of interest is “1”. In this case, the movement range may be set so that the watermark pattern moves in the horizontal direction.

FIG. 3A is a diagram illustrating an example of the relationship between the reference region and the watermark pattern. The moving image data includes four images 301 to 304 corresponding to times t to (t + 3). A block 311 on each image represents a watermark pattern, and a region 312 surrounded by a dotted line is a reference region. An area 313 surrounded by an alternate long and short dash line is a movement range of the watermark pattern. In this example, both the watermark pattern 311 and the reference area 312 have a rectangular shape of 3 × 3 pixels. An enlarged view 311a of the watermark pattern 311 represents the value of each pixel included in the watermark pattern. In this example, each pixel of the watermark pattern 311 has a value of “−2” as shown in the enlarged view 311a. Therefore, the value of the pixel included in the portion where the watermark pattern and the reference region overlap is a value obtained by subtracting “2” from the original pixel value.
In the image 301 at time t, the reference area 312 and the watermark pattern 311 do not overlap. In the image 302 at time (t + 1), the rightmost column in the reference area 312 overlaps with the watermark pattern 311. In the image 303 at time (t + 2), the columns other than the left end of the reference area 312 overlap with the watermark pattern 311. In the image 304 at time (t + 3), the entire reference area 312 overlaps with the watermark pattern 311.

  Enlarged views 312a to 312d of the reference area of each image represent the values of the respective pixels included in the reference area. As shown in the enlarged views 312a to 312d, in the image 302 at time (t + 1), the pixel value in the rightmost column in the reference area corresponds to the pixel value of the watermark pattern in the image 301 at time t. It is smaller by '2'. Also, in the image 303 at time (t + 2), compared to the image 301 at time t, only “2” in which the pixel values included in the columns other than the left end in the reference area correspond to the pixel values of the watermark pattern. It is getting smaller. In the image 304 at time (t + 3), compared to the image 301 at time t, the values of all the pixels in the reference area are smaller by “2” corresponding to the pixel value of the watermark pattern.

  FIG. 3B is a graph showing the change over time of the average value of the pixel values in the reference area, corresponding to FIG. In FIG. 3B, the horizontal axis represents time, and the vertical axis represents pixel values. A graph 320 is a graph representing a temporal change in the average value of the pixel values in the reference area. If the scene in the reference area does not change abruptly, it can be considered that the value of each pixel in the reference area where the watermark pattern is not superimposed does not change in time between several to several tens of images. Therefore, the average value of the pixel values in the reference area changes periodically according to the movement of the watermark pattern. Even if the scene in the reference area changes drastically, if there is no signal that vibrates in the same period as the movement period of the watermark pattern, that is, the fluctuation period of the average pixel value in the reference area, the Fourier spectrum has a watermark pattern. A spectrum with the same period as the movement period of can be observed. In this example, the average value of the pixel values in the reference area temporally varies in a triangular wave shape according to the movement period T of the watermark pattern. At time t when the watermark pattern and the reference area do not overlap, the average value of the pixel values in the reference area becomes the highest, and at the time (t + 3) when the watermark pattern and the reference area completely overlap, The average pixel value is the lowest.

FIG. 4A is a diagram illustrating another example of the relationship between the reference area and the watermark pattern. The moving image data includes four images 401 to 404 corresponding to times t to (t + 3). A block 411 on each image represents a watermark pattern, and a region 412 surrounded by a dotted line is a reference region. An area 413 surrounded by a one-dot chain line is a movement range of the watermark pattern. Also in this example, both the watermark pattern 411 and the reference area 412 have a rectangular shape of 3 × 3 pixels. An enlarged view 411a of the watermark pattern 411 represents the value of each pixel included in the watermark pattern. In this example, each pixel of the watermark pattern 411 has a value of “+2” as shown in the enlarged view 411a. Accordingly, the value of the pixel included in the portion where the watermark pattern and the reference region overlap has a value obtained by adding “2” to the original pixel value.
In the image 401 at time t, the reference area 412 and the watermark pattern 411 do not overlap. In the image 402 at time (t + 1), the uppermost line in the reference area 412 overlaps with the watermark pattern 411. In the image 403 at time (t + 2), the lines other than the lower end of the reference area 412 overlap with the watermark pattern 411. In the image 404 at time (t + 3), the entire reference area 412 overlaps with the watermark pattern 411.

  Enlarged views 412a to 412d of the reference area of each image represent the values of the respective pixels included in the reference area. As shown in the enlarged views 412a to 412d, in the image 402 at time (t + 1), the pixel values in the uppermost row in the reference area correspond to the pixel values of the watermark pattern in the image 401 at time t. It's bigger by '2'. In addition, in the image 403 at time (t + 2), compared to the image 401 at time t, the pixel value included in the row other than the lower end in the reference area is only “2” corresponding to the pixel value of the watermark pattern. It is getting bigger. In the image 404 at time (t + 3), compared to the image 401 at time t, the values of all the pixels in the reference area are increased by “2” corresponding to the pixel value of the watermark pattern.

  FIG. 4B is a graph showing the change over time of the average value of the pixel values in the reference area, corresponding to FIG. In FIG. 4B, the horizontal axis represents time, and the vertical axis represents pixel values. A graph 420 is a graph representing a temporal change in the average value of the pixel values in the reference area. The average value of the pixel values in the reference area changes periodically according to the movement of the watermark pattern. In this example, the average value of the pixel values in the reference area temporally varies in a triangular wave shape according to the movement period T of the watermark pattern. At time t when the watermark pattern and the reference area do not overlap, the average value of the pixel values in the reference area is the lowest, and at the time (t + 3) when the watermark pattern and the reference area completely overlap, The average value of the pixel values is the highest.

  In addition, the watermark pattern position determination unit 21 may set the watermark pattern in a sector shape having a center angle of 270 ° and the center positioned at any one corner of the reference area. In this case, the watermark pattern position determination unit 21 uses the center of the watermark pattern as the rotation axis, and changes the direction in which the watermark pattern is rotated according to the value of the symbol of interest.

FIGS. 5A to 5F are diagrams showing still another example of the relationship between the reference area and the watermark pattern in which the watermark pattern is set in a sector shape as described above. In FIGS. 5A to 5F, a rectangular area 501 indicated by a dotted line is a reference area, and a sector area 502 is a watermark pattern. The center 502a of the watermark pattern is located at the lower right corner of the reference area 501. The moving range of the watermark pattern 502 is a circular region having the center 502a of the watermark pattern 502 as the center and the radius equal to the radius of the watermark pattern 502 regardless of the value of the embedded symbol.
When the value of the embedded symbol is “0”, the watermark pattern position determination unit 21 rotates the watermark pattern clockwise according to the order of FIG. 5A to FIG. 5C. On the other hand, when the value of the embedded symbol is “1”, the watermark pattern position determination unit 21 rotates the watermark pattern counterclockwise in accordance with the order of FIG. 5D to FIG.

The watermark pattern position determination unit 21 determines the position of the watermark pattern in the image of interest based on the position of the watermark pattern in the previous image, the movement direction of the watermark pattern, and a predetermined amount of movement of the image of interest. decide. For this purpose, the watermark pattern position determination unit 21 receives a movement direction flag indicating the position of the watermark pattern and the movement direction of the watermark pattern in the previous image from the movement history recording unit 23. The watermark pattern position determination unit 21 then moves the watermark pattern in the image of interest to the position moved by a predetermined movement amount from the position of the watermark pattern in the previous image along the movement direction represented by the movement direction flag. The position of
For example, as shown in FIG. 3A, it is assumed that the moving range of the watermark pattern is a range in which the reference region is the left end, and the left end of the watermark pattern is the right end at a position adjacent to the right side of the reference region. In this case, when the movement direction of the watermark pattern in the previous image is rightward, the watermark pattern position determination unit 21 moves the watermark pattern to the right by a predetermined movement amount Δ from the position of the watermark pattern in the previous image. Move in the direction. Conversely, when the movement direction of the watermark pattern in the previous image is leftward, the watermark pattern position determination unit 21 moves the watermark pattern leftward by a predetermined movement amount Δ from the position of the watermark pattern in the previous image. Move to.

  The watermark pattern position determining unit 21 notifies the watermark pattern superimposing unit 22 of the position of the watermark pattern in the image of interest. The watermark pattern position determination unit 21 passes a movement direction flag indicating the position of the watermark pattern and the movement direction of the watermark pattern in the image of interest to the movement history recording unit 23. At this time, when the position of the watermark pattern in the image of interest is at any end of the movement range, the watermark pattern position determination unit 21 reverses the movement direction and displays a movement flag indicating the reversed movement direction as a watermark. The data is transferred to the movement history recording unit 23 together with the pattern position. For example, if the watermark pattern is located at the left end of the movement range in the image of interest, the watermark pattern has moved to the left to that image, so the watermark pattern position determination unit 21 sets the movement direction flag. The value is a value indicating the right direction. Then, the watermark pattern position determination unit 21 passes the position of the watermark pattern to the movement history recording unit 23 together with the movement direction flag indicating the right direction.

  Based on the position of the watermark pattern notified from the watermark pattern position determining unit 21, the watermark pattern superimposing unit 22 identifies an area that overlaps the watermark pattern in the image of interest. The watermark pattern superimposing unit 22 corrects the value of each pixel included in the region overlapping the watermark pattern with the value of the corresponding pixel included in the watermark pattern. For example, as shown in FIG. 3A above, when each pixel included in the watermark pattern has a value of “−2”, the watermark pattern superimposing unit 22 sets each pixel included in the region overlapping the watermark pattern. Subtract '2' from the value of.

Note that the watermark pattern superimposing unit 22 may correct the value of only the pixel included in the portion where the watermark pattern and the reference region overlap with the value of the corresponding pixel included in the watermark pattern.
FIG. 6 is a diagram illustrating still another example of the relationship between the reference region and the watermark pattern. In FIG. 6, images 601 to 604 correspond to times t, (t + 1), (t + 2), and (t + 3), respectively. A region 610 surrounded by a dotted line on each image is a reference region, and blocks 611 to 614 represent portions where the watermark pattern and the reference region overlap. In this example, the movement range of the watermark pattern is set along a straight line connecting the upper left corner and the lower right corner of the reference area with respect to a predetermined value of the symbol (for example, '0'). Within the moving range, it moves periodically as time passes. In this case, the watermark pattern moves along a straight line connecting the upper right corner and the lower left corner of the reference area with respect to other values of the symbol.
In the images 601 to 603, only the pixel values included in the portions 611 to 613 in the reference region where the watermark pattern and the reference region 610 overlap are corrected according to the corresponding pixel values included in the watermark pattern. In the image 604, since the entire reference area overlaps the watermark pattern, all the pixels included in the reference area are corrected according to the value of the corresponding pixel included in the watermark pattern.
As described above, by correcting only the value of the pixel included in the portion where the watermark pattern and the reference region overlap, the number of pixels whose value is changed by embedding the digital watermark information is reduced. Therefore, the digital watermark embedding apparatus 1 can suppress a decrease in image quality of moving image data in which digital watermark information is embedded.

The movement history recording unit 23 stores the watermark pattern position and movement direction flag for one image in the storage unit 12. Each time the movement history recording unit 23 receives the watermark pattern position and the movement direction flag from the watermark pattern position determination unit 21, the movement history recording unit 23 sets the value of the watermark pattern position and the movement direction flag stored in the storage unit 12 to the latest value. The watermark pattern position and the moving direction flag value are updated.
Further, the movement history recording unit 23 may store the watermark pattern position and the movement direction flag in the memory circuit of the processing unit 13.
When a plurality of symbols are embedded in one image, the watermark pattern position determining unit 21, the watermark pattern superimposing unit 22, and the movement history recording unit 23 execute the above process for each watermark pattern corresponding to each symbol.

FIG. 7 is an operation flowchart of a digital watermark embedding process controlled by a computer program executed on the processing unit 13 of the digital watermark embedding apparatus 1. The processing unit 13 executes the following digital watermark embedding process for each symbol included in the digital watermark information.
The processing unit 13 sets a symbol of interest among symbols included in the digital watermark information received through the interface unit 11 (step S101). Then, the watermark pattern position determining unit 21 of the processing unit 13 determines the phase or moving direction in the moving period of the watermark pattern according to the value of the symbol of interest included in the digital watermark information (step S102). Since the average pixel value of the reference area changes according to the position of the watermark pattern, the phase of the watermark pattern in the movement period corresponds to the phase of temporal variation of the average pixel value of the reference area. Note that the phase in the movement cycle of the watermark pattern is represented by, for example, an initial position where the watermark pattern is arranged. For example, in a certain reference area, the initial position of the watermark pattern is a position where the watermark pattern completely covers the reference area, and in another reference area, the initial position of the watermark pattern is a position where the watermark pattern does not overlap the reference area. As a result, as the watermark pattern moves, the temporal change of the average pixel in each reference area becomes (dark → light → dark) or (bright → dark → light). Therefore, the phase of the triangular wave representing the time-series change of the average pixel value shown in FIG. 3B differs by π (rad) according to the initial position of the watermark pattern.

The watermark pattern position determination unit 21 sets an image of interest in time order (step S103). The watermark pattern position determination unit 21 determines the position of the watermark pattern in the image of interest based on the position and movement direction flag of the watermark pattern in the previous image and the movement amount of the watermark pattern set in advance ( Step S104). When the image of interest is the first image in the moving image data, the watermark pattern position determination unit 21 arranges a watermark pattern at one end of the movement range of the watermark pattern, for example, The direction toward the other end is the moving direction in the image of interest.
The watermark pattern position determination unit 21 passes the watermark pattern position and movement direction flag in the image of interest to the movement history recording unit 23 of the processing unit 13, and the movement history recording unit 23 receives the watermark pattern position and movement direction flag. It memorize | stores in the memory | storage part 12 (step S105). The watermark pattern position determination unit 21 notifies the watermark pattern superposition unit 22 of the processing unit 13 of the position of the watermark pattern.

The watermark pattern superimposing unit 22 identifies an area overlapping the watermark pattern on the image of interest according to the position of the watermark pattern notified from the watermark pattern position determining unit 21 (step S106). Then, the watermark pattern superimposing unit 22 corrects the value of each pixel included in the area overlapping the watermark pattern according to the value of the corresponding pixel included in the watermark pattern (step S107). Note that, as described above, the watermark pattern superimposing unit 22 may correct only the value of the pixel included in the portion where the watermark pattern and the reference region overlap according to the value of the corresponding pixel included in the watermark pattern.
Thereafter, the processing unit 13 determines whether or not the moving image data has been completed (step S108). If the moving image data has not been completed (No at Step S108), the processing unit 13 repeats the processes at Step S103 to Step S108.
On the other hand, if the moving image data has ended (step S108-Yes), the processing unit 13 ends the digital watermark embedding process.

As described above, this digital watermark embedding apparatus periodically moves a watermark pattern as time elapses according to a phase or a moving direction according to a value of a symbol of interest included in digital watermark information. . Therefore, this digital watermark embedding apparatus can suppress the frosted glass effect caused by embedding digital watermark information because the position of the watermark pattern changes periodically. Therefore, this digital watermark embedding apparatus can suppress degradation of image quality due to embedding digital watermark information and make it difficult for the viewer to visually recognize the embedded digital watermark.
Further, the digital watermark detection device can detect the digital watermark information only by detecting that the average pixel value in the reference region periodically varies from the moving image data in which the digital watermark information is embedded by the digital watermark embedding device. Whether it is embedded or not can be determined. Therefore, even if the moving image data in which the digital watermark information is embedded is duplicated by analog capture, the digital watermark information is not lost as long as the reference area is shown on the image of the duplicated moving image data. Further, the phase or moving direction of the watermark pattern is determined according to the value of the embedded symbol. Therefore, even if processing such as frame rate conversion is performed on moving image data in which digital watermark information is embedded, the phase or movement direction of the watermark pattern does not change, and the digital watermark detection device extracts the embedded digital watermark information. it can.

Next, a digital watermark embedding device according to a second embodiment will be described.
The digital watermark embedding device according to the second embodiment is different from the digital watermark embedding device according to the first embodiment in that a watermark pattern is superimposed after the processing unit randomly converts each image. Therefore, only the differences from the digital watermark embedding apparatus according to the first embodiment will be described below.

FIG. 8 is a block diagram illustrating functions of a processing unit realized for embedding digital watermark information in moving image data according to the second embodiment. In FIG. 8, the same reference numerals as those of the corresponding parts of the processing unit 13 of the digital watermark embedding apparatus 1 according to the first embodiment shown in FIG.
The processing unit 14 includes a random converting unit 24, a watermark pattern position determining unit 21, a watermark pattern superimposing unit 22, a movement history recording unit 23, and an inverse random converting unit 25.

The random conversion unit 24 replaces the pixel arrangement of each image included in the moving image data in a predetermined block unit according to a predetermined conversion rule. The random conversion unit 24 first divides one image into a plurality of blocks, and sets a unique number for each block. For example, the random conversion unit 24 divides the image into m (vertical) × n (horizontal) total (m × n) blocks, and assigns numbers 1 to (m × n) to each block. Next, the random conversion unit 24 executes a scramble process for exchanging the position of each block using the encryption key. For this purpose, the random conversion unit 24 creates a correspondence table that represents the positional relationship between the blocks before and after conversion from the encryption key. For example, assume that the number of the block after conversion is represented by x and the number of the block before conversion is represented by y. At this time, the block conversion formula corresponding to the scramble processing is expressed by the following formula.
In equation (1), p and q are prime numbers represented by the encryption key.

FIG. 9 shows the position of each block on the original image and the blocks in the scrambled image when the original image is divided into 3 vertical blocks × 4 horizontal blocks and p = 7 and q = 13. The relationship with the position of.
In FIG. 9, an image 901 is an original image, and an image 902 is a random converted image obtained by performing a scramble process on the original image 901. The numbers shown in the blocks of the original image 901 and the random transformed image 902 represent the block numbers in the original image. For example, from the equation (1), when x is 1, the corresponding value of y is 7. Therefore, the random conversion unit 24 moves the block with the block number y before conversion to the position of the block with the block number x after conversion of 1 by scramble processing.
Hereinafter, this block, which is a unit for moving the pixel position to another position by scramble processing, is referred to as a scramble block.

The random conversion unit 24 passes the random conversion image to the watermark pattern superimposing unit 22.
The watermark pattern superimposing unit 22 superimposes the watermark pattern at the position determined by the watermark pattern position determining unit 21 on the randomly converted image. At that time, as in the first embodiment, the watermark pattern position determination unit 21 sets the phase or movement direction and movement range of the watermark pattern according to the value of the symbol embedded in the moving image data. In this embodiment, the reference area is set on the random conversion image. Therefore, in order to detect the digital watermark information embedded in the moving image data, the digital watermark detection device only needs to examine the temporal variation of the average pixel value in the reference region on the randomly converted image.
The watermark pattern superimposing unit 22 passes the image subjected to the random conversion and the watermark pattern superimposed thereon to the inverse random conversion unit 25.

  The inverse random conversion unit 25 reproduces an image in which the digital watermark information is embedded by executing an inverse random conversion process on each random converted image on which the watermark pattern is superimposed. Specifically, the inverse random conversion unit 25 performs an inverse scramble process, which is an inverse conversion process of the scramble process executed by the random conversion unit 24, on each image on which the watermark pattern is superimposed. The inverse random conversion unit 25 converts the encryption key and the block position when the scramble process is executed, and uses the equation (1) to scramble the block in the encrypted image where the position of the scramble block after the scramble process is x The original position y of can be determined. Then, the inverse random conversion unit 25 can reproduce the image by moving each scramble block in each image on which the watermark pattern is superimposed to the position of the obtained original scramble block.

The size of the scramble block is preferably smaller than the size of the watermark pattern. By setting the scramble block in this way, the watermark pattern is divided into a plurality of sub-blocks in units of scramble blocks, and each sub-block is diffused in the image. Therefore, it becomes more difficult for the viewer to recognize that the digital watermark information is embedded. When the position of the watermark pattern changes, a part of the watermark pattern overlaps with different scramble blocks before and after the movement of the watermark pattern. Each scramble block is moved to various different positions by inverse random transformation, for example, according to the above equation (1). Therefore, when multiple images that are temporally continuous and have a watermark pattern superimposed thereon are subjected to inverse random transformation, individual sub-blocks included in the watermark pattern appear on the inverse random transformed image as time passes. And move irregularly.
Further, as in the modification of the first embodiment, the watermark pattern superimposing unit 22 performs only the pixel values in the sub-blocks included in the portion where the watermark pattern and the reference area overlap, according to the corresponding pixels of the watermark pattern. May be corrected. In this case, as the time elapses, the number of sub-blocks on the image subjected to inverse random transformation also varies.
As a result, this digital watermark pattern embedding device can better suppress the occurrence of a ground glass effect in moving image data in which the digital watermark pattern is embedded.

  FIG. 10 is a diagram illustrating an example of the relationship between the watermark pattern size and the scramble block size. In this example, the watermark pattern 1000 has a size of 4 pixels in each of the horizontal direction and the vertical direction. On the other hand, the scramble block has a size of 2 pixels in each of the horizontal direction and the vertical direction. Therefore, the watermark pattern 1000 includes four scramble blocks 1001 to 1004.

FIG. 11A shows an example of a random conversion image in which a watermark pattern is embedded, and FIG. 11B shows an image obtained by inverse random conversion of the image shown in FIG.
One watermark pattern 1101 is superimposed on the random converted image 1100 shown in FIG. Also, the horizontal and vertical lengths of the watermark pattern are four times the horizontal and vertical lengths of the scramble block, respectively. That is, 16 scramble blocks are included for one watermark pattern. Therefore, as shown in FIG. 11B, in the image 1110 subjected to inverse random transformation, the watermark pattern 1101 is divided into 16 sub-blocks 1111a to 1111p. Then, the sub blocks 1111a to 1111p are spread over the entire image 1110. For this reason, it is very difficult for the viewer to visually recognize the watermark pattern.

FIG. 12 is an operation flowchart of a digital watermark embedding process controlled by a computer program executed on the processing unit 14 of the digital watermark embedding apparatus. The processing unit 14 executes the following digital watermark embedding process for each symbol included in the digital watermark information.
The processing unit 14 sets a symbol of interest among symbols included in the digital watermark information received through the interface unit 11 (step S201). Then, the random conversion unit 24 of the processing unit 14 randomly converts each image included in the moving image data in which the digital watermark information is embedded (step S202). The random conversion unit 24 passes each randomly converted image to the watermark pattern superimposing unit 22 of the processing unit 14.

Further, the watermark pattern position determination unit 21 of the processing unit 14 determines the phase or movement direction and movement range of the watermark pattern according to the value of the symbol of interest included in the digital watermark information (step S203).
The watermark pattern position determination unit 21 sets an image to be noticed in time order among the plurality of random conversion images (step S204). The watermark pattern position determination unit 21 determines the position of the watermark pattern in the image of interest based on the position and movement direction flag of the watermark pattern in the previous image and the movement amount of the watermark pattern set in advance ( Step S205).
The watermark pattern position determination unit 21 passes the watermark pattern position and movement direction flag in the image of interest to the movement history recording unit 23 of the processing unit 14, and the movement history recording unit 23 stores the watermark pattern position and movement direction flag. The data is stored in the unit 12 (step S206). The watermark pattern position determination unit 21 notifies the watermark pattern superposition unit 22 of the processing unit 14 of the position of the watermark pattern.

The watermark pattern superimposing unit 22 identifies an area overlapping with the watermark pattern on the random converted image of interest according to the position of the watermark pattern notified from the watermark pattern position determining unit 21 (step S207). Then, the watermark pattern superimposing unit 22 corrects the value of each pixel included in the area overlapping the watermark pattern according to the value of the corresponding pixel included in the watermark pattern (step S208). Also in this embodiment, the watermark pattern superimposing unit 22 may correct only the value of the pixel included in the portion where the watermark pattern and the reference region overlap according to the value of the corresponding pixel included in the watermark pattern. The watermark pattern superimposing unit 22 passes the image on which the watermark pattern is superimposed to the inverse random conversion unit 25 of the processing unit 14.
The inverse random conversion unit 25 performs inverse random conversion on the image on which the watermark pattern is superimposed (step S209).

Thereafter, the processing unit 14 determines whether or not the moving image data has been completed (step S210). If the moving image data has not ended (step S210-No), the processing unit 14 repeats the processing of step S204 to step S210.
On the other hand, if the moving image data has ended (step S210-Yes), the processing unit 14 ends the digital watermark embedding process.

  As described above, the digital watermark embedding apparatus according to the second embodiment performs random conversion on the original image, superimposes the watermark pattern, and performs inverse random conversion on the image on which the watermark pattern is superimposed. Therefore, this digital watermark embedding device can suppress the frosted glass effect caused by embedding the digital watermark information because the position of the watermark pattern changes irregularly on the image with time. Therefore, this digital watermark embedding device can suppress degradation of image quality due to embedding digital watermark information and make it difficult for the viewer to visually recognize the embedded digital watermark.

  Note that the inverse random conversion unit in the processing unit of the digital watermark embedding device according to the second embodiment may perform inverse random conversion only on each sub-block included in the watermark pattern. In this case, the watermark pattern superimposing unit of the processing unit specifies an area that overlaps each sub-block included in the watermark pattern subjected to inverse random conversion on the original image not subjected to random conversion. Then, the watermark pattern superimposing unit may correct the value of each pixel in the specified area with the value of the pixel of the corresponding sub-block. As a result, the digital watermark embedding device according to the second embodiment does not need to perform random conversion of the image, so that the processing unit can omit the function of the random conversion unit and can reduce the amount of calculation when embedding the digital watermark information. Can be reduced.

Furthermore, the digital watermark embedding apparatus according to the second embodiment may vary the encryption key according to the value of the symbol embedded in the moving image data. In this case, the watermark pattern position determining unit generates an encryption key according to the value to be embedded, and notifies the random conversion unit and the inverse random conversion unit of the encryption key. The random conversion unit executes the scramble process using the encryption key received from the watermark pattern position determination unit. In addition, the inverse random conversion unit performs the descrambling process using the encryption key received from the watermark pattern position determination unit.
As a result, the digital watermark detection apparatus executes scramble processing for each image using the encryption keys corresponding to the values that can be taken by the embedded symbols. In this case, the digital watermark detection apparatus determines that the value associated with the encryption key used for the one where the watermark pattern having a predetermined shape has been restored from the scrambled image is embedded.

  Next, a digital watermark embedding device according to a third embodiment will be described. In the digital watermark embedding device according to the third embodiment, compared with the digital watermark embedding device according to the second embodiment, the processing unit orthogonally transforms each image included in the moving image data instead of randomly transforming the watermark pattern. Is different in that the image in which is embedded is subjected to inverse orthogonal transform. Therefore, only the differences from the digital watermark embedding apparatus according to the second embodiment will be described below.

FIG. 13 is a block diagram illustrating functions of a processing unit realized for embedding digital watermark information in moving image data according to the third embodiment. In FIG. 13, the same reference numerals as those of the corresponding units of the processing unit 15 of the digital watermark embedding apparatus 1 according to the first embodiment shown in FIG.
The processing unit 15 includes an orthogonal transform unit 26, a watermark pattern position determining unit 21, a watermark pattern superimposing unit 22, a movement history recording unit 23, and an inverse orthogonal transform unit 27.

The orthogonal transform unit 26 performs orthogonal transform on each image. This orthogonal transform can be, for example, Fourier transform, discrete cosine transform, Hadamard transform, or wavelet transform.
The orthogonal transform unit 26 passes the orthogonal transform image to the watermark pattern superimposing unit 22.
The watermark pattern superimposing unit 22 superimposes the watermark pattern at the position determined by the watermark pattern position determining unit 21 on the orthogonal transformation image. At that time, as in the first and second embodiments, the watermark pattern position determining unit 21 determines the phase or moving direction and moving range of the watermark pattern according to the value of the symbol embedded in the moving image data. In this embodiment, the reference area is set on an orthogonally transformed image. Therefore, in order to extract the digital watermark information embedded in the moving image data, the digital watermark detection device only needs to examine the temporal variation of the average pixel value in the reference region on the orthogonal transform image.
The watermark pattern superimposing unit 22 passes the image on which the orthogonal transformation has been performed and the watermark pattern is superimposed to the inverse orthogonal transform unit 27.

  The inverse orthogonal transform unit 27 reproduces an image in which digital watermark information is embedded by performing inverse orthogonal transform on each image on which the watermark pattern is superimposed. Specifically, the inverse orthogonal transform unit 27 performs the inverse transform of the orthogonal transform performed by the orthogonal transform unit 26 on each image on which the watermark pattern is superimposed.

  The operation flow of the digital watermark embedding process by the digital watermark embedding apparatus 3 according to the third embodiment is compared with the operation flow of the digital watermark embedding process according to the second embodiment shown in FIG. Only the processing is different. Specifically, in step S202, the orthogonal transform unit 26 performs orthogonal transform on each image, and in step S210, the inverse orthogonal transform unit 27 performs inverse orthogonal transform on the image in which the watermark pattern is embedded.

  As described above, the digital watermark embedding apparatus according to the third embodiment performs orthogonal transform on the original image, superimposes the watermark pattern, and performs inverse orthogonal transform on the image on which the watermark pattern is superimposed. Therefore, in an image in which digital watermark information is embedded by this digital watermark embedding device and subjected to inverse orthogonal transformation, the frequency component corresponding to the position where the watermark pattern is embedded is only different from the corresponding frequency component of the original image. Therefore, this digital watermark embedding device can suppress degradation of image quality due to embedding digital watermark information and make it difficult for the viewer to visually recognize the embedded digital watermark.

In each of the above embodiments, the value of each pixel of the watermark pattern may be a coefficient that multiplies the pixel value. In this case, the watermark pattern superimposing unit superimposes the watermark pattern by multiplying the value of each pixel included in the area where the watermark pattern and the reference area overlap with the value of the corresponding pixel of the watermark pattern.
In addition, the watermark pattern position determining unit determines the position of the watermark pattern so that the temporal variation of the average pixel value in the reference area becomes a sine wave, or the watermark pattern superimposing unit determines the value of each pixel of the watermark pattern as the watermark pattern. May be changed for each image to be superimposed.
Furthermore, the shape of the reference region is not limited to a square, and may be, for example, a circle, a regular triangle, or a rectangle.
According to still another modification, in each of the above embodiments, the digital watermark embedding apparatus may change both the moving direction and the phase of the watermark pattern according to the value of the embedded symbol.

According to still another modification, a single symbol may take three or more values. In this case, for example, only types of values that can be taken by one symbol are prepared as the types of movement directions of the watermark pattern. For example, when one symbol can take four values of '0', '1', '2', and '3', the watermark pattern position determination unit performs each of '0' to '3' As the movement direction of the watermark pattern, a horizontal direction, a vertical direction, an upper left-lower right direction, and an upper right-lower left direction are set.
The watermark pattern position determination unit may determine the position of the watermark pattern for each image in the moving image data so that the average pixel value in the reference area monotonously increases or decreases monotonously. In this case, for example, the watermark pattern is arranged so as to completely overlap the reference region at the start of the moving image data, and moves in one direction (for example, from top to bottom or from left to right) as time passes.

In another modification, when each symbol is a bit and the digital watermark information is represented by a bit string, the processing unit of the digital watermark embedding apparatus performs error correction coding on the bit string using an error correction code or an error detection code. May be. The processing unit may embed the error correction encoded symbol pattern in the moving image data. For example, the processing unit may use a cyclic redundancy check (CRC) code as an example of an error correction code. In this case, the processing unit may convert the bit string included in the digital watermark information into a CRC code and embed the CRC code in the moving image data. In this case, the variation state of the average pixel value in the reference region may be different depending on the value of the embedded symbol. When a plurality of CRC-encoded symbols are embedded in one image, the digital watermark detection apparatus knows the relationship between the phase of the periodic time variation of the average pixel value of the reference region corresponding to each symbol and the symbol value. Even without it, the value of the embedded symbol can be obtained. Similarly, the digital watermark detection apparatus can obtain the value of the embedded symbol without knowing the relationship between the movement direction of the watermark pattern corresponding to each symbol and the value of the symbol. The digital watermark detection apparatus determines that a value having a remainder of “0” when a bit string extracted from moving image data is divided by a generator polynomial used when generating a CRC code is embedded.
For example, when the divisor that is a generator polynomial is “1011” and the digital watermark information includes the bit string “1110011”, the CRC code corresponding to the bit string is “1110011010”.
In this case, the digital watermark detection apparatus obtains the phase of the movement direction of each watermark pattern or the periodic time variation of the average pixel value of each reference area from the moving image data in which the digital watermark information is embedded. The digital watermark detection apparatus obtains two bit strings “1110011010” and “0001100101” by assigning different symbol values to different movement directions or phases. The digital watermark detection apparatus divides the two bit strings by the divisor “1011” in order to determine whether the bit string extracted from the moving image data is “1110011010” or “0001100101”. Then, the digital watermark detection apparatus can determine that the bit string embedded with '1110011010' with a remainder of '0' is embedded, and by removing the check bit string '010' from the bit string, the embedded bit string Can be requested.

According to still another modification, the digital watermark embedding device includes a plurality of reference regions in order to represent the phase of the periodic temporal variation of the average pixel value in the reference region corresponding to the value of the symbol embedded in the image. It may be set on each image, and one of the reference areas may be set as the specific reference area. Then, the watermark pattern position determination unit of the processing unit determines the position of the watermark pattern so that the watermark pattern always moves within a moving range including the specific reference region at a constant cycle. The watermark pattern set for the specific reference area is hereinafter referred to as a reference pattern.
The watermark pattern position determination unit determines the position of the watermark pattern so that the watermark pattern for the other reference area to which the embedded symbol is assigned also moves in the same cycle as the reference pattern. The watermark pattern position determination unit also calculates the phase difference between the watermark pattern and the reference pattern, that is, the phase difference between the time variation of the average pixel value of the reference region and the time variation of the average pixel value of the specific reference region. Decide according to the value. In this case, the phase in the time variation of each reference region is represented by the phase and phase difference of the average pixel value in the specific reference region.

FIG. 14A is a diagram showing an example of an image in which a plurality of reference areas including a specific reference area are set, and FIG. 14B is set for the image shown in FIG. It is a graph which shows an example of the time change of the average pixel value in each reference field.
Four reference areas 1401 to 1404 are set on the image 1400 shown in FIG. Among these, the reference area 1401 is a specific reference area.
In each graph shown in FIG. 14B, the horizontal axis represents the passage of time, and the vertical axis represents the average pixel value in the reference region. The top graph 1411 represents the temporal variation of the average pixel value in the specific reference area 1401. Graphs 1412 to 1414 represent temporal variations in average pixel values in the reference regions 1402 to 1404, respectively.
In this example, “0” is set as the value of the symbol to be embedded in the reference region 1403 in which the average pixel value varies in the same phase as the temporal variation of the average pixel value in the specific reference region. On the other hand, “1” is set as the value of the symbol to be embedded in the reference areas 1402 and 1404 in which the average pixel value fluctuates by a phase shift of π from the temporal fluctuation of the average pixel value in the specific reference area.

  Next, a digital watermark detection apparatus that detects digital watermark information embedded by the digital watermark embedding apparatus according to each of the above embodiments or modifications thereof will be described.

  FIG. 15 is a schematic configuration diagram of a digital watermark detection apparatus according to one embodiment. The digital watermark detection apparatus 4 includes an interface unit 31, a storage unit 32, and a processing unit 33. The digital watermark embedding device 4 detects the digital watermark information embedded in the moving image data acquired through the interface unit 31.

The interface unit 31 includes, for example, a video signal interface for connecting the digital watermark detection device 4 to a moving image input device (not shown) such as a camcorder and its control circuit. Alternatively, the interface unit 31 may include a communication interface for connecting the digital watermark detection device 4 to a communication network in accordance with a communication standard such as Ethernet (registered trademark) and a control circuit thereof.
The interface unit 31 acquires moving image data via a moving image input device or a communication network, and passes the moving image data to the processing unit 33.
Further, the interface unit 31 may receive the detected digital watermark information from the processing unit 33 and transmit the digital watermark information to another device connected to the digital watermark detection device 4 via the communication network.

  The storage unit 32 includes, for example, at least one of a semiconductor memory, a magnetic disk device, and an optical disk device. The storage unit 32 stores a computer program executed by the digital watermark detection device 4 and various parameters used for detecting digital watermark information embedded in moving image data. For example, the storage unit 32 represents the relationship between the position and range of the reference region, a template representing a frequency component corresponding to the time variation period of the average pixel value of the reference region, and the movement direction of the watermark pattern and the embedded value. Store the lookup table. The storage unit 32 may store detected digital watermark information. Further, the storage unit 32 may store moving image data in which digital watermark information is embedded.

  The processing unit 33 includes one or a plurality of processors, a memory circuit such as a random access memory, and a peripheral circuit. The processing unit 33 detects digital watermark information embedded in the moving image data. Further, the processing unit 33 controls the entire digital watermark detection apparatus 4.

FIG. 16 is a block diagram illustrating functions of a processing unit realized for detecting digital watermark information on moving image data.
The processing unit 33 includes a conversion unit 41, an average pixel value calculation unit 42, a watermark pattern detection unit 43, a watermark pattern phase / movement direction detection unit 44, and a digital watermark information extraction unit 45. Then, the processing unit 33 acquires the moving image data via the interface unit from, for example, a camcorder that has captured the moving image data in which the digital watermark information is embedded or another device that stores the moving image data. Then, the processing unit 33 analyzes the moving image data and detects embedded digital watermark information.

  The conversion unit 41 receives each image included in the moving image data in which the digital watermark information is embedded from the processing unit 33 in chronological order. Then, the conversion unit 41 corrects image distortion due to distortion aberration or the like of the imaging optical system of the imaging apparatus that captured the moving image data for each image. For this purpose, the conversion unit 41 first detects an area where a moving image is actually shown on the image. In addition, the area | region where the moving image is actually reflected is called a moving image area | region below for convenience.

For this purpose, the conversion unit 41 detects an edge of the image using, for example, a sobel filter or a Laplacian filter. For example, the conversion unit 41 sets the longest edge in the upper half of the image among the edges that are substantially horizontal in the horizontal direction as the upper end of the moving image area. Also, the conversion unit 41 sets the longest edge in the lower half of the image among the edges that are substantially horizontal to the lower end of the moving image area. Furthermore, for example, the converting unit 41 sets the longest edge in the left half of the image as the left end of the moving image region and the longest edge in the right half of the image as the right end of the moving image region among the edges that are substantially vertical. To do. Note that the conversion unit 41 may use the upper end of the image as the upper end of the moving image area if the maximum length of the edge in the substantially horizontal direction in the upper half of the image is, for example, ½ or less of the horizontal width of the image. . Further, the conversion unit 41 may use the lower end of the image as the lower end of the moving image area if the maximum length of the edge in the substantially horizontal direction in the lower half of the image is, for example, 1/2 or less of the horizontal width of the image. . Further, the conversion unit 41 may set the left edge of the image as the left edge of the moving image area if the maximum length of the edge in the substantially vertical direction in the left half of the image is, for example, ½ or less of the vertical height of the image. . Similarly, the conversion unit 41 sets the right edge of the image as the right edge of the moving image area if the maximum length of the edge in the substantially vertical direction in the right half of the image is, for example, ½ or less of the vertical height of the image. Also good.
The conversion unit 41 geometrically transforms the moving image area so that the upper and lower ends of the moving image area become straight lines parallel to each other and the left and right ends become straight lines parallel to each other. Note that when the processing unit 16 can acquire distortion data of the imaging optical system of the imaging apparatus that has captured the moving image data in which the digital watermark information is embedded, the moving image region is set so as to cancel the distortion. Nonlinear geometric transformation may be performed.
Further, the converting unit 41 moves the moving image so that the number of pixels in the horizontal direction and the vertical direction of the moving image area is equal to the number of pixels in the horizontal direction and the vertical direction of each image of the moving image data in which the digital watermark information is embedded. The region may be resampled.

The conversion unit 41 generates a converted image by executing the same conversion process as the conversion process executed by the conversion unit of the digital watermark embedding apparatus on the moving image area. For example, when the digital watermark embedding apparatus randomly converts each image, the conversion unit 41 also randomly converts the moving image area detected from each image. Note that even when only the watermark pattern is subjected to inverse random transformation, the conversion unit 41 performs a random transformation process that is an inverse transformation of the inverse random transformation on the moving image area. Alternatively, when the digital watermark embedding apparatus orthogonally transforms each image, the conversion unit 41 also orthogonally transforms the moving image area.
The conversion unit 41 passes the converted images to the average pixel value calculation unit 42 and the watermark pattern phase / movement direction detection unit 44 in time series order.
Note that, when the watermark pattern is directly superimposed on each image included in the moving image data, such as the moving image data generated by the digital watermark embedding device according to the first embodiment, the converting unit 41 displays the moving image region. Is a converted image.

The average pixel value calculation unit 42 specifies a predetermined region as a reference region in each converted image received in chronological order. The average pixel value calculation unit 42 calculates an average pixel value in the reference area. Note that when a plurality of reference areas are set on one image, the average pixel value calculation unit 42 calculates an average pixel value for each reference area.
The average pixel value calculation unit 42 passes the average pixel value of the reference area and the position of the reference area on each converted image to the watermark pattern detection unit 43 in time series.

The watermark pattern detection unit 43 determines whether or not the watermark pattern is superimposed on the converted image by detecting temporal variation of the average pixel value for each reference region.
As described above, since the watermark pattern moves periodically, the temporal variation of the average pixel value in the reference region has a frequency component in the time axis direction corresponding to the movement cycle of the watermark pattern. For example, when the average pixel value in the reference region varies in a triangular wave shape in time series, the frequency component of the average pixel value in the time axis direction includes a specific frequency component corresponding to the triangular wave. Therefore, the watermark pattern detection unit 43 creates a one-dimensional vector in which the average pixel values of the reference region are arranged in time series for the reference region of interest, and Fourier-transforms the one-dimensional vector. Then, the watermark pattern detection unit 43 extracts only the spectrum having the same frequency as the triangular wave from the obtained frequency component. If the extracted spectrum is close to the triangular wave spectrum (for example, within a range of 1/2 to 2 times the triangular wave spectrum), the watermark pattern detection unit 43 superimposes the watermark pattern on the target reference region. Is determined. On the other hand, when the extracted spectrum is significantly different from the spectrum of the triangular wave (for example, twice or more), it is determined that a signal having the same period as the triangular wave is superimposed on the image. Therefore, the watermark symbol extracted from the reference position may contain an error. At this time, the watermark pattern detection unit 43 may notify the watermark pattern phase / movement direction detection unit 44 that the watermark has been lost.
Alternatively, the watermark pattern detection unit 43 obtains a difference in average pixel values between two converted images that are temporally continuous with respect to the reference region of interest. The watermark pattern detection unit 43 may determine that the watermark pattern is superimposed on the reference region of interest when the difference periodically changes over time.
The watermark pattern detection unit 43 notifies the watermark pattern phase / movement direction detection unit 44 of the position of the reference area determined to have the watermark pattern superimposed thereon.

The watermark pattern phase / movement direction detection unit 44 detects the phase of the temporal variation of the average pixel value and / or the movement direction of the watermark pattern in the reference region where the watermark pattern detection unit 43 determines that the watermark pattern is superimposed. To detect.
For this purpose, the watermark pattern phase / movement direction detection unit 44 checks all phases or movement directions that may be set in the reference area. In order to inspect the phase, the watermark pattern phase / movement direction detection unit 44 creates a one-dimensional vector in which the average pixel values of the reference region are arranged in chronological order, and detects the phase of the average pixel value with respect to time variation. .

Further, in order to inspect the moving direction, the watermark pattern phase / moving direction detection unit 44 obtains a difference in pixel value between adjacent pixels along the moving direction. The watermark pattern phase / movement direction detection unit 44 sets the movement direction in which the difference value varies with time as the movement direction set for the watermark pattern.
For example, if the value of the embedded symbol is '1', the movement direction set for the watermark pattern is the vertical direction, and if the value of the embedded symbol is '0', It is assumed that the moving direction set in this way is the horizontal direction. In this case, the watermark pattern phase / movement direction detection unit 44 obtains the average pixel value of each column in the vertical direction within the reference area for each image and determines whether the movement direction is the horizontal direction or not. A difference value of average pixel values between columns is obtained as a vertical direction difference value. Further, the watermark pattern phase / movement direction detection unit 44 obtains an average pixel value of each line in the horizontal direction within the reference area for each image to determine whether or not the movement direction is the vertical direction, and between adjacent lines. The difference value of the average pixel value is obtained as the horizontal direction difference value. Then, the watermark pattern phase / movement direction detection unit 44 determines that the watermark pattern is moving along the movement direction corresponding to the time-variable difference value between the vertical direction difference value and the horizontal direction difference value. To do.

When the phase of the temporal variation of the average pixel value in the reference area is specified by the difference between that phase and the phase of the temporal variation of the average pixel value in the specific reference area, the watermark pattern phase / movement direction detection unit 44 Find the phase difference. For this purpose, the watermark pattern phase / movement direction detector 44 creates, for example, one-dimensional vectors in which the average pixel values of the reference region and the specific reference region are arranged in time series, and detects the phase. Then, the watermark pattern phase / movement direction detection unit 44 obtains a difference between the phase of the temporal variation of the average pixel value in the reference region and the phase of the temporal variation of the average pixel value in the specific reference region.
The watermark pattern phase / movement direction detection unit 44 notifies the digital watermark information extraction unit 45 of the movement direction of the watermark pattern and the phase or phase difference of the average pixel value over time.

  The digital watermark information extraction unit 45 calculates a symbol pattern that can be taken from the phase of temporal variation of the average pixel value in each reference region. For example, if the symbol is a bit, the digital watermark information extraction unit 45 creates two types of patterns with “0” or “1” for each reference region symbol having the same phase. Then, the digital watermark information extraction unit 45 selects a symbol pattern that is determined to have no error in the inspection using the CRC code. For example, when the phases of three reference positions are different from 0 degrees, 180 degrees (π rad), and 0 degrees, possible symbol patterns are (0,1,0) or (1,0,1) It is. As described above, which pattern is correct as the symbol pattern is determined by performing CRC check at the time of symbol determination by embedding a CRC check parity in advance as a watermark symbol. Alternatively, when the phase of temporal variation of the average pixel value of each reference region is specified by the difference between the phase and the phase of temporal variation of the average pixel value of the specific reference region, the digital watermark information extracting unit 45 A reference table representing the relationship between the phase difference and the symbol value is read from the storage unit 32. Then, the digital watermark information extraction unit 45 refers to the reference table to obtain a value corresponding to the phase difference detected by the watermark pattern phase / movement direction detection unit 44.

  Alternatively, the digital watermark information extraction unit 45 reads from the storage unit 32 a reference table that represents the relationship between the movement direction of the watermark pattern and the value of the embedded symbol. The digital watermark information extraction unit 45 refers to the reference table to obtain a value corresponding to the movement direction of the watermark pattern detected by the watermark pattern phase / movement direction detection unit 44. Then, the digital watermark information extraction unit 45 sets the value as the value of the symbol embedded in the moving image data. The digital watermark information extraction unit 45 reproduces the digital watermark information by obtaining the values of symbols embedded in chronological order.

FIG. 17 is an operation flowchart of a digital watermark detection process controlled by a computer program executed on the processing unit 33 of the digital watermark detection apparatus 4. Note that the processing unit 33 executes the following processing for each symbol included in the digital watermark information embedded in the moving image data.
The processing unit 33 selects a plurality of images included in the moving image data (step S301).
The conversion unit 41 of the processing unit 33 selects so that the shape and the number of pixels of the selected moving image area of each image are equal to the shape and the number of pixels of the image included in the moving image data in which the digital watermark is embedded. Correct each image. Furthermore, when the watermark pattern is subjected to inverse random transformation or inverse orthogonal transformation by the digital watermark embedding device, the conversion unit 41 generates a transformed image by performing random transformation or orthogonal transformation on the image (step S302). Then, the conversion unit 41 passes the converted image to the average pixel value calculation unit 42 of the processing unit 33.

The average pixel value calculation unit 42 calculates the average pixel value in the reference area in each converted image (step S303). The average pixel value calculation unit 42 passes the average pixel value in the reference area to the watermark pattern detection unit 43.
The watermark pattern detection unit 43 determines whether or not the average pixel value in the reference region varies with time (step S304). When the average pixel value does not vary with time (No in step S304), the watermark pattern detection unit 43 determines that the watermark pattern is not superimposed. The watermark pattern detection unit 43 notifies the processing unit 33 to that effect. Thereafter, the processing unit 33 ends the digital watermark information detection process.

On the other hand, when the average pixel value fluctuates with time (step S304—Yes), the watermark pattern detection unit 43 determines that the watermark pattern is superimposed on each converted image. The watermark pattern detection unit 43 notifies the determination result that the watermark pattern is superimposed to the watermark pattern phase / movement direction detection unit 44 of the processing unit 33.
The watermark pattern phase / movement direction detector 44 detects the phase of temporal variation of the average pixel value in the reference area and / or the movement direction of the watermark pattern (step S305). The watermark pattern phase / movement direction detection unit 44 notifies the digital watermark information extraction unit 45 of the processing unit 33 of the phase and / or movement direction.
The digital watermark information extraction unit 45 refers to a reference table representing the correspondence relationship between the phase of the temporal variation of the average pixel value or the movement direction of the watermark pattern and the embedded value, and determines a value corresponding to the phase or movement direction. The symbol value is detected (step S306). At that time, the digital watermark information extraction unit 45 performs error correction decoding processing on each of the possible symbol patterns, determines an error-free pattern, and embeds each symbol included in the error-free pattern. The detected symbol value may be detected.
Then, the processing unit 33 ends the digital watermark detection process.
If a plurality of reference areas are set for one converted image, the processing unit 33 executes the processes of steps S303 to S306 for each reference area.

The moving image data in which the digital watermark information is embedded by the digital watermark embedding device may be a color image. For example, when the moving image data has luminance information for each of three colors of red (R), green (G), and blue (B), the digital watermark embedding device according to each embodiment uses any color. The above-described electronic watermark embedding process may be executed. The digital watermark detection apparatus may perform the above-described digital watermark detection process for the color in which the digital watermark information is embedded.
According to another modification, the watermark pattern position determination unit of the digital watermark embedding apparatus may assign a plurality of images included in a predetermined period to one symbol included in the digital watermark information. In this case, the digital watermark embedding apparatus can embed a plurality of symbols in the time series direction in the moving image data. The predetermined period is set to, for example, 1 to several times the moving period of the watermark pattern. In this case, each time the period corresponding to one symbol embedded in the moving image data ends, the watermark pattern superimposing unit applies a predetermined pattern indicating a symbol delimiter until the period corresponding to the next symbol starts. It may be superimposed on.
Also, in this case, the digital watermark detection apparatus detects the change in the average pixel value in the reference region for each predetermined period and the phase difference or the movement direction of the watermark pattern for the change in the average pixel value. A plurality of symbols embedded in is detected. Note that the digital watermark detection apparatus can specify a predetermined period by detecting a predetermined pattern indicating a symbol delimiter by, for example, pattern matching.

  The digital watermark embedding device according to each of the above embodiments is incorporated in, for example, a set top box, a server, or a personal computer. Then, the device in which the digital watermark embedding device is incorporated, for example, executes the above-described digital watermark embedding processing when reproducing the moving image data with respect to the moving image data that is the video content received via the communication network or the antenna. To do. When the moving image data is compressed according to a predetermined compression method, the device decodes each image included in the moving image data according to the predetermined compression method. Then, the apparatus stores each image included in the moving image data in a buffer memory included in the apparatus in chronological order. Then, the apparatus reads images from the buffer memory in chronological order, executes digital watermark embedding processing, and displays the image in which the digital watermark information is embedded on the display.

  Furthermore, a computer program that causes a computer to realize each function of the processing unit of the digital watermark embedding device according to each of the above embodiments may be provided in a form recorded on a computer-readable medium. Similarly, a computer program that causes a computer to realize the functions of the processing unit of the digital watermark detection apparatus according to the above-described embodiment may be provided in a form recorded on a computer-readable medium.

  All examples and specific terms listed herein are intended for instructional purposes to help the reader understand the concepts contributed by the inventor to the present invention and the promotion of the technology. It should be construed that it is not limited to the construction of any example herein, such specific examples and conditions, with respect to showing the superiority and inferiority of the present invention. Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and modifications can be made thereto without departing from the spirit and scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Digital watermark embedding apparatus 11 Interface part 12 Memory | storage part 13,14,15 Processing part 21 Watermark pattern position determination part 22 Watermark pattern superimposition part 23 Movement history recording part 24 Random transformation part 25 Reverse random transformation part 26 Orthogonal transformation part 27 Reverse orthogonality Conversion unit 4 Digital watermark detection device 31 Interface unit 32 Storage unit 33 Processing unit 41 Conversion unit 42 Average pixel value calculation unit 43 Watermark pattern detection unit 44 Watermark pattern phase / movement direction detection unit 45 Digital watermark information extraction unit

Claims (9)

An interface unit for acquiring moving image data and digital watermark information;
A processing unit that embeds the digital watermark information in the moving image data,
A watermark pattern that includes a plurality of pixels and is superimposed on each image in the moving image data includes at least a part of a reference region set at a predetermined position on each image in the moving image data. The average pixel value of the reference region that is moved according to the value of the symbol included in the digital watermark information with the passage of time within the movement range and is superimposed by the watermark pattern as the watermark pattern moves is a period. A watermark pattern position determining function for determining the position of the watermark pattern so as to change periodically,
A watermark pattern superimposing function for correcting the value of each pixel included in an area where the reference area and the watermark pattern overlap, according to the value of the corresponding pixel of the watermark pattern;
A processing unit for realizing
An electronic watermark embedding device. The reference region set for each of the plurality of images in the moving image data is on a random conversion image obtained by random conversion in which each pixel of the image is replaced with another pixel in a predetermined block unit according to a predetermined conversion rule. Set to
The processing unit further realizes an inverse random conversion function for performing an inverse random conversion that is an inverse conversion of the random conversion on pixels included in an area where the reference area set on the random conversion image and the watermark pattern overlap. ,
The watermark pattern superimposing function converts, for each of a plurality of images in the moving image data, a pixel value that overlaps a pixel included in the watermark pattern that has been subjected to the inverse random transformation into a pixel value that has undergone the inverse random transformation. The digital watermark embedding apparatus according to claim 1, wherein correction is performed in response. The processing unit orthogonally transforms each of the plurality of images in the moving image data to generate an orthogonally transformed image, and an inverse orthogonal transform that is an inverse transform of the orthogonal transform for each orthogonally transformed image Further implements an inverse orthogonal transform function to perform
The reference area set for each of a plurality of images in the moving image data is set to a predetermined area on each orthogonal transform image,
The watermark pattern superimposing function corrects the value of each pixel included in an area where the reference area and the watermark pattern set on each orthogonal transform image overlap according to the value of the corresponding pixel of the watermark pattern. The digital watermark embedding apparatus according to claim 1. The electronic device according to any one of claims 1 to 3, wherein the watermark pattern position determination function sets a moving direction of the watermark pattern to be different for each symbol value included in the digital watermark information. Watermark embedding device.   The watermark pattern position determination function sets a phase for a periodic change of the average pixel value in which the reference area is superimposed by a watermark pattern according to a symbol value included in the digital watermark information, and sets the phase to the phase. The digital watermark embedding apparatus according to claim 1, wherein the position of the watermark pattern in each of the plurality of images is determined accordingly. Obtain moving image data and digital watermark information,
A watermark pattern that includes a plurality of pixels and is superimposed on each image in the moving image data includes at least a part of a reference region set at a predetermined position on each image in the moving image data. The average pixel value of the reference area superimposed by the watermark pattern moves periodically according to the value of the symbol included in the digital watermark information as time elapses within the movement range. Determining the position of the watermark pattern to change to
Correcting the value of each pixel included in an area where the reference area and the watermark pattern overlap according to the value of the corresponding pixel of the watermark pattern;
An electronic watermark embedding method including the above. An electronic watermark embedding computer program that causes a computer to embed electronic watermark information in moving image data,
A watermark pattern that includes a plurality of pixels and is superimposed on each image in the moving image data includes at least a part of a reference region set at a predetermined position on each image in the moving image data. The average pixel value of the reference area superimposed by the watermark pattern moves periodically according to the value of the symbol included in the digital watermark information as time elapses within the movement range. Determining the position of the watermark pattern to change to
Correcting the value of each pixel included in an area where the reference area and the watermark pattern overlap according to the value of the corresponding pixel of the watermark pattern;
A computer program that causes a computer to execute. An interface unit for acquiring moving image data in which digital watermark information is embedded;
A processing unit for detecting the digital watermark information embedded in the moving image data,
For each image included in the moving image data, a pixel value averaging function for calculating an average pixel value in a reference area set at a predetermined position of each image;
Corresponds to symbols included in the digital watermark information when the average pixel value in the reference area varies with time, and included in a symbol pattern encoded using an error correction code or error detection code A watermark pattern detection function for determining that a watermark pattern to be embedded in each of the images;
A watermark phase detection function for determining a phase of change of an average pixel value in the reference region;
All symbol patterns that can be taken from the phase difference are calculated, and among the symbol patterns, symbol values that are included in a symbol pattern that has no error when decoded according to the error correction code or error detection code A digital watermark information extraction function that takes the value of a symbol contained in the digital watermark information as
A processing unit for realizing
An electronic watermark detection apparatus comprising: An interface unit for acquiring moving image data in which digital watermark information is embedded;
A processing unit for detecting the digital watermark information embedded in the moving image data,
For each image included in the moving image data, a pixel value averaging function for calculating an average pixel value in a reference area set at a predetermined position of each image;
A watermark pattern detection function for determining that a watermark pattern corresponding to a symbol included in the digital watermark information is embedded in each image when an average pixel value in the reference region varies with time;
A watermark pattern movement direction detection function for specifying the movement direction of the watermark pattern based on temporal variation of the value of each pixel included in the reference region;
A value corresponding to the moving direction of the watermark pattern is included in the digital watermark information with reference to a reference table representing a correspondence relationship between the moving direction of the watermark pattern and a value that a symbol included in the digital watermark information can take. A digital watermark information extraction function as a symbol value;
A processing unit for realizing
An electronic watermark detection apparatus comprising: